Thermoplastic resins such as polyesters are used for a variety of purposes taking advantage of their excellent mechanical properties, moldability, heat resistance, weather resistance, light fastness and chemical resistance. With advancing technology in recent years, however, even more superior properties are being required for resins depending on their intended uses. Recently, such demanded properties are increasingly being achieved by techniques using “nanocomposites”, or compositions having laminar compounds dispersed on the nanoscale in thermoplastic resins. Formation of nanocomposites can realize improvement in a variety of properties, including enhanced high heat resistance, high elasticity, flame retardance and gas barrier performance (for example, see Nakajo K., “The World of Nanocomposites”, Kogyo Chosakai, 2000). Laminar compounds must be dispersed on the nanoscale in order to form nanocomposites, and several different methods have been attempted. For example, for production of a polyester composite material having a laminar compound dispersed on a monolayer level, there has been disclosed the use of an organic cation having a functional group which is reactive with the polyester monomer, as an organic modified form of the laminar compound (Japanese Unexamined Patent Publication HEI No. 9-48908). There has also been described a polyester resin composition comprising a uniformly dispersed molten mixture of a layered silicate in a polyester resin, while maintaining a layer structure of 5-20 layers with an interlaminar distance of 15-35 Å (Japanese Unexamined Patent Publication No. 2001-261947). In addition, Japanese Unexamined Patent Publication No. 2003-327851 describes a process for production of a laminar inorganic crystal-polymer composite by freeze-drying of a swelling laminar inorganic crystal and impregnation thereof in a molten polymer. However, nanocomposites which employ polyesters cannot achieve the same degree of dispersion as polyamides, and therefore improvement in dispersibility has been desired.